The onion nobody likes

SUMMER SCHEDULE: Now is the time to get delicious summer vegetables into the ground to take advantage of warm temperatures which promote growth. Plant capsicum, chillies, cucumbers, lettuce, tomatoes, zucchini and more.

Onion weed is evident in a number of gardens now and it is one of the more difficult weeds to control in the home garden.

Some gardeners may not realise that the small white flowers that appear at the top of tall, slender, light green stems are actually from the onion weeds.

The flowers could easily be mistaken for a spring-flowering bulb. However, crushing the stem will reveal the onion-type odour that is present. The leaves of the plant are long, narrow and flat in the same colour as the flowering stem.

It is fairly easy to eradicate onion weed from lawns by keeping the grass growing vigorously. Healthy lawn grass will out-compete onion weed in a fairly short time and no other treatment is necessary. In fact, onion weed in lawns is merely a sign that the lawn needs a bit more care and attention.

Onion weed is a perennial, storing nutrients and carbohydrates in its bulbs to generate growth the following season. This is the same process used by daffodils and other spring flowering bulbs.

It is the bulbs that create difficulties in attempts at eradication. If the leaves of the plant are pulled or dug up, they usually break away from the bulb underneath, or only the parent bulb is removed.

Small bulbs (bulbils) are released from the main bulb and each of these will then form new plants. Therefore, attempts at eradication of onion weed by digging it up will only result in spreading the plants.

Treating the leaves with a glysophate-based preparation will only kill the parent bulb. The use of normal strength herbicides is also usually ineffective.

Some gardeners use undiluted glysophate sprays but this can cause other problems in the garden. Glyphosate is not broken down on contact with soil and binds to certain soil compounds. When soil conditions change, it can become unbound and affect later crops. Soil-borne plant diseases are also more common where herbicides are used.

The main principle to observe in attempting to eradicate onion weed from the garden is preventing the bulbs storing food for growth. It is also important to remember that persistence in treatment options will be necessary, probably over several seasons.

An immediate partial control involves removing the flower heads before they set seed, and disposing of them. Cutting the foliage off at ground level will prevent the plants making carbohydrates in their leaves.

If the weeds are present in an unused part of the garden, the plants can be slashed or mown, with the area then covered in black plastic for several months.

Onion weed that is present in the average garden bed, with other plants, is much more difficult to eradicate.

Cut off the foliage at ground level with shears to prevent it making food for the bulbs. Then mulch the beds with five to seven centimetres of mulch. It may be necessary to cut back foliage several times as soon as it appears.

If this process is undertaken consistently, bulb growth will become progressively weaker, and the problem will eventually be eliminated without disturbing the soil and stimulating the growth of more bulbs.

Injecting vegetable oil carefully into the soil around the bulbs, causing them to suffocate and then die down, may be an alternate method of removal.

DECEPTIVE: Onion weed can often be mistaken for a spring bulb. However it is a pest which, thanks to its bulbils, can prove hard to eradicate and may take several seasons.

Planting Plan

October is the month when summer vegetables should be planted out, as they require warmth for good growth.

Prior to planting, the soil should be improved using well-rotted mushroom compost, cow manure or, preferably, compost from the compost heap.

Vegetables require large amounts of organic food if they are to produce their best crops.

As fast-growing plants require lime in their leaf margins, adding lime to the soil will encourage healthy leaves as well as assisting in the prevention of blossom-end rot in tomatoes.

Although the days may be warmer, cooler night temperatures will retard growth of the vegetables.

Some gardeners prefer to grow their plants from seed. If the temperatures are a bit cooler, this will delay seed germination, so it may be preferable to grow the seeds in trays or punnets, rather than planting them directly into the ground. The tray or punnet can then be placed in a warmer position.

Seeds require constant access to air, moisture, warmth and sunlight for them to germinate satisfactorily. Placing seeds in a specially-prepared seed-raising mixture will be beneficial.

Once the seeds have emerged, they should be gradually hardened off, that is, they should be gradually exposed to normal outdoor temperatures, rather than planting them directly into the garden bed.

If preferred, the seeds can be placed into containers of potting mix, enriched with some plant food, before they are placed into the garden. An appropriate time to do this would be when the plants have two or three true leaves.

However, some vegetables will have better germination rates if sown directly into the garden. These include peas, corn, sunflowers and carrots.

Mix fine carrot seeds with fine sand for easier and more successful planting.